1. Field of the Invention
The present invention relates to a rotary compressor used for an air conditioner, for example.
2. Description of the Related Art
FIG. 7 is an enlarged cross sectional view illustrating first and second compression units of a conventional rotary compressor, and FIG. 8 is an enlarged cross sectional view of D portion of FIG. 7. As illustrated in FIG. 7 and FIG. 8, the conventional rotary compressor has a compression unit 52 which includes annular cylinders 521S, 521T in which suction ports (not illustrated) and vane grooves 528S, 528T are radially provided to the side portion thereof, and an end plate (not illustrated) which covers end portions of the cylinders 521S, 521T, annular pistons 125S, 125T which fit into eccentric portions 152S, 152T of a rotary shaft rotated by a motor and revolve in the cylinders 521S and 521T along cylinder inner walls 523S, 523T of the cylinders 521S, 521T and form actuation chambers 130S, 130T between the cylinder inner walls 523S, 523T, and vanes 127S, 127T which protrude into the actuation chambers 130S, 130T from insides of vane grooves 528S, 528T provided in the cylinders 521S, 521T so as to abut against the annular pistons 125S, 125T and divide the actuation chambers 130S, 130T into suction chambers 131S, 131T, and compression chambers 133S, 133T, wherein discharge ports 190S, 190T which discharge compressed refrigerants in the compression chambers 133S, 133T outside the compression chambers 133S, 133T are provided near the vane grooves 528S, 528T of end plates (not illustrated), and notch portions 537S, 537T which guide compressed refrigerants in the compression chambers 133S, 133T to the discharge ports 190S, 190T are provided near the vane grooves 528S, 528T of the cylinders 521S, 521T.
A rotary compressor which has the above-stated configurations has had a problem that after the annular pistons 125S, 125T revolve in the cylinders 521S, 521T and pass through the discharge ports 190S, 190T, in small spaces 538S, 538T surrounded by the cylinder inner walls 523S, 523T, the annular pistons 125S, 125T, and the vanes 127S, 127T, refrigerant gas which is not discharged from the discharge ports 190S, 190T is compressed resulting in over compression loss which causes decrease in compression effect and worsening of COP.
Conventionally, a closed compressor (rotary compressor) including a closed container and electric elements and compression elements contained in the closed container, the compression elements being composed of a cylinder having an actuation chamber inside the cylinder, a roller (annular piston) which rotates in the cylinder by an eccentric portion of a rotary shaft thereof, a vane which contacts with the roller and slides a guide groove provided in the cylinder so as to divide the actuation chamber of the cylinder into a compression chamber and a suction chamber, and a frame (end plate) which seals the actuation chamber of the cylinder, the frame being provided with a discharge port which communicates with the compression chamber of the cylinder, wherein the discharge port is located completely inside the compression chamber of the cylinder and shaped in a circle, a long hole, or a crescent which does not protrude inside of an inner circumferential edge of the roller, moreover, the roller is shaped in a cylinder or a cylinder whose end face portion at the discharge port side is thick is disclosed (for example, refer to Japanese Patent Application Laid-open No. 05-133363.)
Additionally, a closed rotary compressor enclosing a motor unit and a rotary compression mechanism connected to the motor unit via a rotary shaft in a closed case, the rotary compression mechanism including a cylinder which forms a cylinder chamber, first and second cover members provided on both end faces of the cylinder so as to cover the cylinder chamber, and a roller and a vane which separate the cylinder chamber interior into a compression chamber and a suction chamber, wherein a discharge port for discharging a refrigerant compressed in the cylinder chamber is provided in at least one of the first and second cover members, provided a cross sectional area of the compression chamber when the vane is in a lower dead position is B (m2) and a cross sectional area of the discharge port is C (m2), the discharge port is set so as to satisfy C/B≦0.15, and the length of the discharge port is set to be 3 mm or less, moreover, a proportion of area that the discharge port faces the cylinder chamber is set to be 87% or more of the cross sectional area of the discharge port, and the cylinder is not provided with a notch groove for refrigerant discharge, is disclosed (for example, refer to Japanese Patent Application Laid-open No. 2007-198319.)
However, according to the conventional art disclosed in Japanese Patent Application Laid-open No. 05-133363, since the discharge port is located completely inside the compression chamber of the cylinder and a discharge notch is not provided in the compression chamber of the cylinder, although it is possible to decrease re-expansion loss, after the roller passes through the discharge port, refrigerant gas which is not discharged is compressed resulting in over compression loss in a space surrounded by the inner wall of the cylinder, the roller, and the vane, and the high pressure refrigerant gas returns to the suction chamber side of low pressure, causing decrease in compression effect and worsening of COP, which must be the problem.
Moreover, according to the conventional art disclosed in Japanese Patent Application Laid-open No. 2007-198319, since the proportion of area that the discharge port faces the cylinder chamber is 87% or more of the cross sectional area of the discharge port, volume of the space surrounded by the inner wall of the cylinder, the roller, and the vane after the roller passes through the discharge port decreases compared with that of Japanese Patent Application Laid-open No. 05-133363 so that the over compression loss slightly decreases, but still, the compression effect decreases and the COP of the whole refrigeration cycle worsens.
The present invention has been made considering the above-stated matters and aims to decrease the over compression loss and improve the compression effect so as to obtain a rotary compressor with better COP.